1. Field of the Invention
This invention relates to the removal of heat from electronic components, and in particular to the attachment of a heat sink to a component having a ball grid array (BGA) serving as contacts.
2. Description of Related Art
The efficient removal of heat from operating electronic components is a widespread problem which is addressed by various methods of convection and conduction heat transfer. Thermal performance is also enhanced by using components with integral heat spreaders where the die is attached directly to one side of a heat spreader whose other side is the upper exterior of the component. This can improve heat dissipation by a factor of two, but an additional heat sink is needed where the power dissipation exceeds four watts.
Other factors to consider are the supporting printed wiring board's layout, mounting technology, space availability, and the intended life time of the product. The wiring layout can be complicated where holes need to be drilled through the printed wiring board to mount components or heat sinks. Surface mount technology has been developed to avoid holes, save space, and to simplify and automate assembly by using a reflow soldering process which is well known. The inputs/outputs (I/Os) of the component terminate in solder balls on the underside of the BGA component. Their number can exceed 500 per component, and they are arranged in a ball grid array. The attachment of any heat sink for greater thermal performance must be compatible with surface mount technology.
The reliability and lifetime of semiconductor junctions are inversely related to the junction temperature. Service lifetimes of less than a decade have been acceptable for consumer electronics because upgrades in software have caused obsolescence in relatively inexpensive apparatus. For industrial applications such as the telecommunications industry, however, the large capital expense associated with the introduction of a new system requires a minimum lifetime of 20 years. The increased complexity of these systems, therefore the number of dissipating junctions per chip, also requires the dissipation of heat in excess of four watts per component.
Accordingly, there is a need in the art for a heat sink and attachment process that is compatible with ball grid array components assembled with surface mount technology which also meets the performance and reliability requirements of the telecommunications industry.